Obesity is widely regarded as one of the greatest public health crises of our time. Yet there is another health risk heavier people face that won't appear on their medical charts: anti-fat prejudice. In fact, discrimination against heavy people, by the general public and medical professionals, might be a greater health and social problem than any extra pounds they may be carrying.

Despite the fact that body weight is largely determined by an individual's biology, genetics and social environment, medical providers often blame patients for their weight and blame their weight for any health problems they have. When I was doing research for a book on social perceptions of fat, one woman told me about how she visited a vascular surgeon because she had developed a superficial blood clot after a fall and her primary doctor had recommended an ultrasound to make sure there wasn't a deeper problem.

The surgeon never asked about her relevant medical history, including whether she smoked or was on birth-control pills, or how long she had had varicose veins, she told me. Instead, he took one look at her, concluded that she fell because of her weight and began talking up fen-phen, a weight-loss drug that has since been banned. Scores of studies have shown that medical providers typically regard fat patients as lazy, self-indulgent and noncompliant. As a result, heavy patients don't always receive the health care they deserve.

It's similar to racial profiling - when police, for example, are more likely to suspect that a person of color has committed a crime. For health professionals dealing with overweight patients, this tendency could be considered "size profiling": They assume that a person has - or will develop - a particular ailment because he or she is heavy. Neither form of profiling necessarily intends to discriminate, but both involve judging people based on generalizations about a group to which they belong. Both types of profiling lead to false positives (people wrongfully accused or medically overtreated) and false negatives (people who get away or are medically undertreated).

Many heavy women told me that doctors routinely blamed any ailment, from a fall to a sore throat, on their weight. Studies document this pattern. Convinced that a patient's weight is the underlying problem and that the patient can control his or her physique, many doctors don't conduct the diagnostic tests they would otherwise perform on a thin person. Instead, they tell their heavy patients to lose weight or recommend weight-loss surgery. In many cases, such size profiling leads to problems that could have been avoided with proper diagnostic tests.

I don't deny that there are health risks associated with higher body mass. The clearest case is Type 2 diabetes, which becomes more likely as weight goes up. Yet, as many medical researchers have pointed out, it's not clear whether obesity causes diabetes, whether diabetes causes obesity or whether both conditions are caused by a third factor, such as poor nutrition, stress or genetics. Moreover, the association between weight and Type 2diabetes is not perfect. Some thin people develop the disease, and many fat people never will.

A 2008 study estimated the proportion and number of Americans in the "normal weight," "overweight" and "obese" categories who were metabolically healthy or abnormal, based on their blood pressure, triglycerides, cholesterol, glucose, insulin resistance and inflammation.

On average, heavier people were more likely to have metabolic abnormalities, but there were plenty of exceptions. Almost a quarter of normal-weight people had abnormal profiles, while more than half of overweight people and almost a third of obese people had normal profiles. Treating weight as a proxy for health could result in underdiagnosis of more than 16 million normal-weight Americans and overdiagnosis of almost 56 million overweight and obese Americans.

These numbers speak to the scope of the problem, but they don't capture the personal trauma. One woman I talked to visited a new gynecologist, who, during her annual exam, began lecturing her about her weight. When the patient said she did not want to discuss weight loss, the doctor backed off. She resumed her lecture, however, during the pelvic exam, when the patient had her feet in stirrups and a speculum inside her. She told me she felt as if she were mentally "going somewhere else" - not unlike how many women feel while being sexually abused.

Distressing experiences such as this lead many heavy women to avoid doctors' offices altogether. As a result, fat women are less likely to get Pap smears and other important medical screenings, and have higher rates of cervical cancer and other preventable illnesses. One study even showed that many doctors refuse to perform Pap smears on heavier women.

For insurers, weight is a reason to deny health-care coverage by classifying "morbid obesity" as a preexisting condition. While the Patient Protection and Affordable Care Act will make it illegal to deny health insurance based on preexisting conditions, the new law allows employers to charge overweight employees higher insurance premiums.

Anti-fat attitudes also take an emotional toll. For instance, fat children are more likely than their thinner peers to be bullied. And weight-based bullying does not end with childhood: Women speak of young men hurling insults or even food at them in public spaces. Fear of such humiliation leads many heavy women to avoid exercising in public. In extreme cases, these women might not go out at all, depriving them of the face-to-face social interaction that is vital for mental and physical well-being.

We know that anti-fat prejudice harms average-size and thin people as well, as the fear of becoming fat drives many of them to develop eating disorders and body-image problems.

Yet, the way we talk about fatness as a medical issue and a public health crisis brought on largely by reckless personal choices may be worsening anti-fat prejudice and related health problems. Public health campaigns, product ads and news reports about the "obesity epidemic" often feature images of headless torsos with overflowing guts, intended to elicit disgust, or fat children looking forlornly into the camera.

Messages about the need to wage war on fat are everywhere. First lady Michelle Obama has made eliminating childhood obesity the biggest issue on her agenda. Starting in 2011, Children's Healthcare of Atlanta ran an aggressive ad campaign that included billboards with fat children blankly staring at viewers, accompanied by captions such as "Chubby kids may not outlive their parents." Even Coca-Cola, whose sugary drinks are widely regarded as a major contributor to weight gain, has a new advertisement reminding consumers that "all calories count."

Do such messages inspire people to lose weight? We don't know. However, they seem likely to reinforce perceptions that overweight people are ugly, lazy, unhealthy and unlovable. Could these campaigns make fat children feel worse about themselves than they already do? Might they even make bullies and weight bigots feel justified?

To test this theory, I conducted several controlled experiments with a psychologist and a UCLA sociology graduate student. We found that people who read news reports that discuss obesity as a public health crisis were more likely to agree with stereotypes of fat people as unlikable, untrustworthy and less intelligent than thinner people, compared with those who hadn't read such articles.

Other studies have shown that individuals who think people can control their weight are more likely to believe that weight-based discrimination is justified. And my research has found that news media discussions of obesity overwhelmingly blame personal choices - rather than social or biological factors - for Americans' rising weights.

In our rush to cure the obesity epidemic, we are not only ignoring but may be worsening anti-fat prejudice and size profiling. If medical professionals want to improve public health, they might start by renewing their pledge to "first, do no harm" by treating patients of all sizes with dignity and respect.

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Abigail Saguy, an associate professor and vice chair of sociology at UCLA, is the author of "What's Wrong With Fat?"